Displaying publications 61 - 80 of 94 in total

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  1. Mohd Nor NA, Abdul Razak I, Ab-Murat N, Ismail N, Ibrahim F
    MyJurnal
    Tobacco usage among dental students and the amount of training they received may have an impact on tobacco cessation activities undertaken for their patients. This study aims to assess Malaysian dental students’ tobacco use, exposure to second-hand smoke and their attitude towards tobacco control activities and curriculum. This was a cross-sectional study using a self-administered questionnaire adapted from the Global Health Professions Students Survey (GHPSS). The questionnaire was distributed to all Malaysian fourth and fifth year
    dental students in four public dental schools (n=372), namely University of Malaya (UM), Universiti Teknologi Mara (UiTM), Universiti Kebangsaan Malaysia (UKM) and Universiti Sains Islam Malaysia (USIM). The data were analysed using descriptive and chi square tests. In total, (n=349) respondents completed the questionnaire, yielding a 93.8% response rate. Although the prevalence of Malaysian dental students who ‘ever smoked’ was 21.2%, the prevalence of current smokers was low (2.3%). About 62% and 39% of students reported having been exposed to second-hand smoke in public and at home, respectively. USIM students were significantly less likely to recall having received training about approaches to smoking cessation (52.9%, p<0.001). Significantly fewer smokers than nonsmokers agreed on tobacco banning policy. Regardless of their smoking status, the majority of dental students showed positive attitudes towards dentists’ role in tobacco cessation. Tobacco user among Malaysian dental students was low. There were statistically significant differences between ever smokers and non-smokers’ attitudes towards tobacco banning policy. The majority of dental students showed positive attitudes towards dentists’ role in
    tobacco cessation.
    Keywords: Attitudes; GHPSS; public health; smoking; tobacco
  2. Barabino G, Frize M, Ibrahim F, Kaldoudi E, Lhotska L, Marcu L, et al.
    Sci Eng Ethics, 2020 02;26(1):275-292.
    PMID: 30806940 DOI: 10.1007/s11948-019-00097-0
    The aim of this article is to offer a view of the current status of women in medical physics and biomedical engineering, while focusing on solutions towards gender balance and providing examples of current activities carried out at national and international levels. The International Union of Physical and Engineering Scientists in Medicine is committed to advancing women in science and health and has several initiatives overseen by the Women in Medical Physics and Biomedical Engineering Task Group. Some of the main strategies proposed by the Task Group to attain gender balance are: (a) identify and promote female role models that achieve successful work-life balance, (b) establish programs to develop female leaders, (c) create opportunities for females to increase the international visibility within the scientific community, and (d) establish archives and databases of women in STEM.
  3. Habib MA, Ibrahim F, Mohktar MS, Kamaruzzaman SB, Lim KS
    Clin Neurophysiol, 2020 03;131(3):642-654.
    PMID: 31978849 DOI: 10.1016/j.clinph.2019.11.058
    OBJECTIVE: This study aimed to present a new ictal component selection technique, named as recursive ICA-decomposition for ictal component selection (RIDICS), for potential application in epileptogenic zone localization.

    METHODS: The proposed technique decomposes ictal EEG recursively, eliminates a few unwanted components in every recursive cycle, and finally selects the most significant ictal component. Back-projected EEG, regenerated from that component, was used for source estimation. Fifty sets of simulated EEGs and 24 seizures in 8 patients were analyzed. Dipole sources of simulated-EEGs were compared with a known dipole location whereas epileptogenic zones of the seizures were compared with their corresponding sites of successful surgery. The RIDICS technique was compared with a conventional technique.

    RESULTS: The RIDICS technique estimated the dipole sources at an average distance of 12.86 mm from the original dipole location, shorter than the distances obtained using the conventional technique. Epileptogenic zones of the patients, determined by the RIDICS technique, were highly concordant with the sites of surgery with a concordance rate of 83.33%.

    CONCLUSIONS: Results show that the RIDICS technique can be a promising quantitative technique for ictal component selection.

    SIGNIFICANCE: Properly selected ictal component gives good approximation of epileptogenic zone, which eventually leads to successful epilepsy surgery.

  4. Mat S, Tan MP, Mohktar MS, Kamaruzzaman SB, Ibrahim F
    Eur J Clin Nutr, 2021 Oct 07.
    PMID: 34620997 DOI: 10.1038/s41430-021-01020-2
    OBJECTIVE: To evaluate the role of PhA in diabetes in a large population of older adults with a high prevalence of diabetes in order to gain new insights on the potential diagnostic and prognostic role of PhA in individuals with diabetes.

    DESIGN: Cross-sectional study.

    SETTING: Teaching Hospital.

    PARTICIPANTS: 1085 individuals aged 55 years or over.

    MEASUREMENTS: Phase Angle was obtained using bioimpedance analysis with the Bodystat QuadScan® 4000. Diabetes mellitus was considered present with fasting hyperglycaemia (serum fasting glucose >6.66 mmol/l), HbA1c > 42 mmol/mol (6.1%), or self-reported Diabetes or the consumption of glucose-lowering agents.

    RESULTS: The mean age of the (standard deviation) of the 1,085 participants was 68.11 (7.12) years and 60.7% were women. Among male participants, individuals with PhA within the lowest quartile (PhA ≤4.9) were significantly more likely to have diabetes mellitus [odds Ratio (95% confidence interval, CI), 2.02 (1.17-3.47)] following adjustments for age, body mass index and other comorbidities. The above relationship was attenuated following further adjustment hypoglycaemic medications. Men on oral hypoglycaemic agents had significantly reduced PhA [mean difference (95% CI), -0.44 (-0.67 to -0.22)]. No significant relationship between PhA and diabetes existed among women.

    CONCLUSION: The association between lower PhA (≤4.9) in men aged 55 and over and diabetes which is accounted for by oral hypoglycaemic agents. The mechanisms underlying this relationship remain unclear. This relationship should also be evaluated further to determine the potential of PhA as a prognostic tool for diabetes.

  5. Nawi AM, Ismail R, Ibrahim F, Hassan MR, Manaf MRA, Amit N, et al.
    BMC Public Health, 2021 Nov 13;21(1):2088.
    PMID: 34774013 DOI: 10.1186/s12889-021-11906-2
    BACKGROUND: Drug abuse is detrimental, and excessive drug usage is a worldwide problem. Drug usage typically begins during adolescence. Factors for drug abuse include a variety of protective and risk factors. Hence, this systematic review aimed to determine the risk and protective factors of drug abuse among adolescents worldwide.

    METHODS: Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) was adopted for the review which utilized three main journal databases, namely PubMed, EBSCOhost, and Web of Science. Tobacco addiction and alcohol abuse were excluded in this review. Retrieved citations were screened, and the data were extracted based on strict inclusion and exclusion criteria. Inclusion criteria include the article being full text, published from the year 2016 until 2020 and provided via open access resource or subscribed to by the institution. Quality assessment was done using Mixed Methods Appraisal Tools (MMAT) version 2018 to assess the methodological quality of the included studies. Given the heterogeneity of the included studies, a descriptive synthesis of the included studies was undertaken.

    RESULTS: Out of 425 articles identified, 22 quantitative articles and one qualitative article were included in the final review. Both the risk and protective factors obtained were categorized into three main domains: individual, family, and community factors. The individual risk factors identified were traits of high impulsivity; rebelliousness; emotional regulation impairment, low religious, pain catastrophic, homework completeness, total screen time and alexithymia; the experience of maltreatment or a negative upbringing; having psychiatric disorders such as conduct problems and major depressive disorder; previous e-cigarette exposure; behavioral addiction; low-perceived risk; high-perceived drug accessibility; and high-attitude to use synthetic drugs. The familial risk factors were prenatal maternal smoking; poor maternal psychological control; low parental education; negligence; poor supervision; uncontrolled pocket money; and the presence of substance-using family members. One community risk factor reported was having peers who abuse drugs. The protective factors determined were individual traits of optimism; a high level of mindfulness; having social phobia; having strong beliefs against substance abuse; the desire to maintain one's health; high paternal awareness of drug abuse; school connectedness; structured activity and having strong religious beliefs.

    CONCLUSION: The outcomes of this review suggest a complex interaction between a multitude of factors influencing adolescent drug abuse. Therefore, successful adolescent drug abuse prevention programs will require extensive work at all levels of domains.

  6. Muniandy S, Dinshaw IJ, Teh SJ, Lai CW, Ibrahim F, Thong KL, et al.
    Anal Bioanal Chem, 2017 Nov;409(29):6893-6905.
    PMID: 29030671 DOI: 10.1007/s00216-017-0654-6
    Reduced graphene oxide (rGO) has emerged as a promising nanomaterial for reliable detection of pathogenic bacteria due to its exceptional properties such as ultrahigh electron transfer ability, large surface to volume ratio, biocompatibility, and its unique interactions with DNA bases of the aptamer. In this study, rGO-azophloxine (AP) nanocomposite aptasensor was developed for a sensitive, rapid, and robust detection of foodborne pathogens. Besides providing an excellent conductive and soluble rGO nanocomposite, the AP dye also acts as an electroactive indicator for redox reactions. The interaction of the label-free single-stranded deoxyribonucleic acid (ssDNA) aptamer with the test organism, Salmonella enterica serovar Typhimurium (S. Typhimurium), was monitored by differential pulse voltammetry analysis, and this aptasensor showed high sensitivity and selectivity for whole-cell bacteria detection. Under optimum conditions, this aptasensor exhibited a linear range of detection from 108 to 101 cfu mL-1 with good linearity (R 2 = 0.98) and a detection limit of 101 cfu mL-1. Furthermore, the developed aptasensor was evaluated with non-Salmonella bacteria and artificially spiked chicken food sample with S. Typhimurium. The results demonstrated that the rGO-AP aptasensor possesses high potential to be adapted for the effective and rapid detection of a specific foodborne pathogen by an electrochemical approach. Graphical abstract Fabrication of graphene-based nanocomposite aptasensor for detection of foodborne pathogen.
  7. Abdulrahman SA, Rampal L, Othman N, Ibrahim F, Hayati KS, Radhakrishnan AP
    Patient Prefer Adherence, 2017;11:1273-1284.
    PMID: 28794617 DOI: 10.2147/PPA.S141609
    BACKGROUND: Inconsistent literature evidence suggests that sociodemographic, economic, and system- and patient-related factors are associated with clinic attendance among the HIV-positive population receiving antiretroviral therapy (ART) around the world. We examined the factors that predict outpatient clinic attendance among a cohort of HIV-positive patients initiating ART in Selangor, Malaysia.

    PATIENTS AND METHODS: This cross-sectional study analyzed secondary data on outpatient clinic attendance and sociodemographic, economic, psychosocial, and patient-related factors among 242 adult Malaysian patients initiating ART in Selangor, Malaysia. Study cohort was enrolled in a parent randomized controlled trial (RCT) in Hospital Sungai Buloh Malaysia between January and December 2014, during which peer counseling, medication, and clinic appointment reminders were provided to the intervention group through short message service (SMS) and telephone calls for 24 consecutive weeks. Data on outpatient clinic attendance were extracted from the hospital electronic medical records system, while other patient-level data were extracted from pre-validated Adult AIDS Clinical Trial Group (AACTG) adherence questionnaires in which primary data were collected. Outpatient clinic attendance was categorized into binary outcome - regular attendee and defaulter categories - based on the number of missed scheduled outpatient clinic appointments within a 6-month period. Multivariate regression models were fitted to examine predictors of outpatient clinic attendance using SPSS version 22 and R software.

    RESULTS: A total of 224 (93%) patients who completed 6-month assessment were included in the model. Out of those, 42 (18.7%) defaulted scheduled clinic attendance at least once. Missed appointments were significantly more prevalent among females (n=10, 37.0%), rural residents (n=10, 38.5%), and bisexual respondents (n=8, 47.1%). Multivariate binary logistic regression analysis showed that Indian ethnicity (adjusted odds ratio [AOR] =0.235; 95% CI [0.063-0.869]; P=0.030) and heterosexual orientation (AOR =4.199; 95% CI [1.040-16.957]; P=0.044) were significant predictors of outpatient clinic attendance among HIV-positive patients receiving ART in Malaysia.

    CONCLUSION: Ethnicity and sexual orientation of Malaysian patients may play a significant role in their level of adherence to scheduled clinic appointments. These factors should be considered during collaborative adherence strategy planning at ART initiation.

    Study site: Outpatient clinic, Hospital Sungai Buloh Malaysia
  8. Sayad A, Ibrahim F, Mukim Uddin S, Cho J, Madou M, Thong KL
    Biosens Bioelectron, 2018 Feb 15;100:96-104.
    PMID: 28869845 DOI: 10.1016/j.bios.2017.08.060
    Outbreaks of foodborne diseases have become a global health concern; hence, many improvements and developments have been made to reduce the risk of food contamination. We developed a centrifugal microfluidic automatic wireless endpoint detection system integrated with loop mediated isothermal amplification (LAMP) for monoplex pathogen detection. Six identical sets were designed on the microfluidic compact disc (CD) to perform 30 genetic analyses of three different species of foodborne pathogens. The consecutive loading, mixing, and aliquoting of the LAMP primers/reagents and DNA sample solutions were accomplished using an optimized square-wave microchannel, metering chambers and revulsion per minute (RPM) control. We tested 24 strains of pathogenic bacteria (Escherichia coli, Salmonella spp and Vibrio cholerae), with 8 strains of each bacterium, and performed DNA amplification on the microfluidic CD for 60min. Then, the amplicons of the LAMP reaction were detected using the calcein colorimetric method and further analysed via the developed electronic system interfaced with Bluetooth wireless technology to transmit the results to a smartphone. The system showed a limit of detection (LOD) of 3 × 10-5ngμL-1 DNA by analysing the colour change when tested with chicken meat spiked with the three pathogenic bacteria. Since the entire process was performed in a fully automated way and was easy to use, our microdevice is suitable for point-of-care (POC) testing with high simplicity, providing affordability and accessibility even to poor, resource-limited settings.
  9. Wan-Fei K, Hassan STS, Sann LM, Ismail SIF, Raman RA, Ibrahim F
    Electron Physician, 2017 Aug;9(8):4924-4933.
    PMID: 28979724 DOI: 10.19082/4924
    BACKGROUND: Depression and anxiety are common in stroke survivors as well as their family caregivers. However, it is not known whether each person's emotional distress contributes to their partner's quality of life (QOL).

    OBJECTIVE: This study aimed to examine the effect of depression and anxiety on QOL in stroke survivor-caregiver dyads using dyadic analysis technique - the Actor-Partner Interdependence Model (APIM).

    METHODS: This was a cross-sectional pilot study with a total of 30 participating dyads (30 stroke survivors and 30 family caregivers) from Hospital Rehabilitasi Cheras, Kuala Lumpur, Malaysia. This pilot study was conducted over a period of 3 months, between December 2014 and February 2015. Depression and anxiety were assessed using the Hospital Anxiety and Depression Scale (HADS). QOL was assessed using the Short Form-12 Health Survey (SF-12). All analyses were carried out using IBM SPSS version 22. Dyadic data were analysed using multilevel modelling (MLM).

    RESULTS: Depression was uniquely associated with an individual's own QOL. Survivors and caregivers with higher depression had poorer physical component summary (PCS) scores and mental component summary (MCS) scores. Stroke survivor's depression exerted a significant actor effect on their PCS (b=-1.42, p=0.001) and MCS (b=-1.52, p<0.001). Caregiver's depression exerted a significant actor effect on their PCS (b=-2.53, p<0.001) and MCS (b=-1.51, p=0.004). Caregivers' anxiety negatively influenced their own MCS (b=-0.58, p=0.031). Furthermore, depression exerted a significant partner effect on PCS in stroke survivors (b=-1.19, p=0.003). Caregivers' depression was also related to their stroke survivors' poorer QOL, particularly PCS.

    CONCLUSION: The findings suggest that depression affects the QOL of both stroke survivors and caregivers, not only emotionally but also physically. This dyadic study also has evidence pointing to depression in caregivers and its association with stroke survivors' physical QOL.

  10. Yasin ZAM, Ibrahim F, Rashid NN, Razif MFM, Yusof R
    Curr Pharm Biotechnol, 2017;18(11):864-876.
    PMID: 29256348 DOI: 10.2174/1389201019666171219105920
    BACKGROUND: Skin is the largest and most visible organ of the body. Many of its functions include temperature regulation, immunity from microorganisms, maintaining electrolyte balance, and protection from physical injuries, chemical agents and ultraviolet (UV) radiation. Aging occurs in every layer of the skin, primarily due to the degradation of its components. Induction of degradative enzymes and the abundant production of reactive oxygen species lead to skin aging. Understanding the complexity of skin structure and factors contributing to the skin aging will help us impede the aging process. Applications of anti-aging products are a common method to prevent or repair damages that lead to aging.

    CONCLUSION: This review will provide information on the causes and indicators of skin aging as well as examine studies that have used plants to produce anti-aging products.

  11. Thiha A, Ibrahim F, Muniandy S, Dinshaw IJ, Teh SJ, Thong KL, et al.
    Biosens Bioelectron, 2018 Jun 01;107:145-152.
    PMID: 29455024 DOI: 10.1016/j.bios.2018.02.024
    Nanowire sensors offer great potential as highly sensitive electrochemical and electronic biosensors because of their small size, high aspect ratios, and electronic properties. Nevertheless, the available methods to fabricate carbon nanowires in a controlled manner remain limited to expensive techniques. This paper presents a simple fabrication technique for sub-100 nm suspended carbon nanowire sensors by integrating electrospinning and photolithography techniques. Carbon Microelectromechanical Systems (C-MEMS) fabrication techniques allow fabrication of high aspect ratio carbon structures by patterning photoresist polymers into desired shapes and subsequent carbonization of resultant structures by pyrolysis. In our sensor platform, suspended nanowires were deposited by electrospinning while photolithography was used to fabricate support structures. We have achieved suspended carbon nanowires with sub-100 nm diameters in this study. The sensor platform was then integrated with a microfluidic chip to form a lab-on-chip device for label-free chemiresistive biosensing. We have investigated this nanoelectronics label-free biosensor's performance towards bacterial sensing by functionalization with Salmonella-specific aptamer probes. The device was tested with varying concentrations of Salmonella Typhimurium to evaluate sensitivity and various other bacteria to investigate specificity. The results showed that the sensor is highly specific and sensitive in detection of Salmonella with a detection limit of 10 CFU mL-1. Moreover, this proposed chemiresistive assay has a reduced turnaround time of 5 min and sample volume requirement of 5 µL which are much less than reported in the literature.
  12. Vitus V, Ibrahim F, Shamsuddin SAA, Razali N, Noor Azlan NAB, Zaman WSWK
    Polymers (Basel), 2022 Dec 15;14(24).
    PMID: 36559856 DOI: 10.3390/polym14245489
    Carbon derived from biomass waste usage is rising in various fields of application due to its availability, cost-effectiveness, and sustainability, but it remains limited in tissue engineering applications. Carbon derived from human hair waste was selected to fabricate a carbon-based bioscaffold (CHAK) due to its ease of collection and inexpensive synthesis procedure. The CHAK was fabricated via gelation, rapid freezing, and ethanol immersion and characterised based on their morphology, porosity, Fourier transforms infrared (FTIR), tensile strength, swelling ability, degradability, electrical conductivity, and biocompatibility using Wharton’s jelly-derived mesenchymal stem cells (WJMSCs). The addition of carbon reduced the porosity of the bioscaffold. Via FTIR analysis, the combination of carbon, agar, and KGM was compatible. Among the CHAK, the 3HC bioscaffold displayed the highest tensile strength (62.35 ± 29.12 kPa). The CHAK also showed excellent swelling and water uptake capability. All bioscaffolds demonstrated a slow degradability rate (<50%) after 28 days of incubation, while the electrical conductivity analysis showed that the 3AHC bioscaffold had the highest conductivity compared to other CHAK bioscaffolds. Our findings also showed that the CHAK bioscaffolds were biocompatible with WJMSCs. These findings showed that the CHAK bioscaffolds have potential as bioscaffolds for tissue engineering applications.
  13. Tharshini NK, Ibrahim F, Kamaluddin MR, Rathakrishnan B, Che Mohd Nasir N
    Int J Environ Res Public Health, 2021 Aug 17;18(16).
    PMID: 34444412 DOI: 10.3390/ijerph18168663
    In addition to social and environmental factors, individual personality traits have intricately linked with maladaptive behaviour. Thus, the purpose of this article was to review the link between individual personality traits and criminality. A systematic review was conducted to obtain information regarding the link between individual personality traits with criminal behaviour in the Sage, Web of Science, APA PsycNet, Wiley Online Library, and PubMed databases. The results indicate that individual personality traits that contribute towards criminality are (i) psychopathy; (ii) low self-control; and (iii) difficult temperament. As an overall impact, the review is expected to provide in-depth understanding of the link between individual personality traits and criminality; hence, greater consideration will be given to the dimension of personality as a notable risk factor of criminal behaviour.
  14. Popović ŽV, Thiha A, Ibrahim F, Petrović BB, Dahlan NA, Milić L, et al.
    Sci Rep, 2023 Dec 02;13(1):21277.
    PMID: 38042878 DOI: 10.1038/s41598-023-48379-9
    Intraoral theranostics, the integration of diagnostics and therapeutics within the oral cavity, is gaining significant traction. This pioneering approach primarily addresses issues like xerostomia (dry mouth), commonly resulting from cancer treatment, with a specific focus on monitoring temperature and humidity. This paper introduces the innovative Intra-Oral Portable Micro-Electronic (IOPM) fluidic theranostic device platform. It leverages conventional dental spoons by incorporating advanced sensors for precise measurements of oral temperature and humidity. Personalization options include a microfluidic chip and a tooth model, enabling targeted delivery of therapeutic agents to optimize treatment outcomes. The electronic control system simplifies the administration of fluid dosages, intelligently adjusted based on real-time oral cavity temperature and humidity readings. Rigorous experimental evaluations validate the platform's precision in delivering fluid volumes at predefined intervals. This platform represents a transformative advancement for individuals contending with oral health challenges such as xerostomia (dry mouth). Furthermore, it has the potential to elevate oral healthcare standards by providing advanced diagnostics and tailored therapeutic solutions, benefiting both patients and dental professionals alike.
  15. Aboodarda SJ, Shariff MA, Muhamed AM, Ibrahim F, Yusof A
    J Hum Kinet, 2011 Dec;30:5-12.
    PMID: 23487250 DOI: 10.2478/v10078-011-0067-0
    This study was designed to quantify and compare Electromyographic activity (EMG) and applied load in quadriceps muscle within performing high intensity knee extension exercises by Elastic Resistance (ER) and Nautilus Machine (NM). Sixteen male and female subjects (22.4 ± 4.7 yrs) completed 8 RM seated knee extension by NM, elastic tubing with original length (E0) and elastic tubing with 30% decrement of original length (E30). The mean value of EMG and external force were calculated and synchronized across various segments of motion for the three modes of training. The results demonstrated that in the early concentric and late eccentric segments of contraction, NM elicited significantly higher muscle activation than both E30 and E0 (p < 0.05). However, in the mid-concentric and mid-eccentric as well as late concentric and early eccentric segments no significant differences were observed between NM and E30. These findings supported the approach that developing external recoil of force in ER device by reducing 30% of initial length of elastic material can offer similar neuromuscular activation compared with NM. On this basis, E30 can be suggested as an affordable and non-gym based exercise device which has the capacity to provide an appropriate high resistance stimulus to meet the training requirement of athletes.
  16. Habib MA, Mohktar MS, Kamaruzzaman SB, Lim KS, Pin TM, Ibrahim F
    Sensors (Basel), 2014 Apr 22;14(4):7181-208.
    PMID: 24759116 DOI: 10.3390/s140407181
    This paper presents a state-of-the-art survey of smartphone (SP)-based solutions for fall detection and prevention. Falls are considered as major health hazards for both the elderly and people with neurodegenerative diseases. To mitigate the adverse consequences of falling, a great deal of research has been conducted, mainly focused on two different approaches, namely, fall detection and fall prevention. Required hardware for both fall detection and prevention are also available in SPs. Consequently, researchers' interest in finding SP-based solutions has increased dramatically over recent years. To the best of our knowledge, there has been no published review on SP-based fall detection and prevention. Thus in this paper, we present the taxonomy for SP-based fall detection and prevention solutions and systematic comparisons of existing studies. We have also identified three challenges and three open issues for future research, after reviewing the existing articles. Our time series analysis demonstrates a trend towards the integration of external sensing units with SPs for improvement in usability of the systems.
  17. Aeinehvand MM, Ibrahim F, Harun SW, Al-Faqheri W, Thio TH, Kazemzadeh A, et al.
    Lab Chip, 2014 Mar 07;14(5):988-97.
    PMID: 24441792 DOI: 10.1039/c3lc51116b
    Centrifugal microfluidic platforms have emerged as point-of-care diagnostic tools. However, the unidirectional nature of the centrifugal force limits the available space for multi-step processes on a single microfluidic disc. To overcome this limitation, a passive pneumatic pumping method actuated at high rotational speeds has been previously proposed to pump liquid against the centrifugal force. In this paper, a novel micro-balloon pumping method that relies on elastic energy stored in a latex membrane is introduced. It operates at low rotational speeds and pumps a larger volume of liquid towards the centre of the disc. Two different micro-balloon pumping mechanisms have been designed to study the pump performance at a range of rotational frequencies from 0 to 1500 rpm. The behaviour of the micro-balloon pump on the centrifugal microfluidic platforms has been theoretically analysed and compared with the experimental data. The experimental data show that the developed pumping method dramatically decreases the required rotational speed to pump liquid compared to the previously developed pneumatic pumping methods. It also shows that within a range of rotational speed, a desirable volume of liquid can be stored and pumped by adjusting the size of the micro-balloon.
  18. Hosseini S, Azari P, Farahmand E, Gan SN, Rothan HA, Yusof R, et al.
    Biosens Bioelectron, 2015 Jul 15;69:257-64.
    PMID: 25765434 DOI: 10.1016/j.bios.2015.02.034
    Electrospun polyhydroxybutyrate (PHB) fibers were dip-coated by polymethyl methacrylate-co-methacrylic acid, poly(MMA-co-MAA), which was synthesized in different molar ratios of the monomers via free-radical polymerization. Fabricated platfrom was employed for immobilization of the dengue antibody and subsequent detection of dengue enveloped virus in enzyme-linked immunosorbent assay (ELISA). There is a major advantage for combination of electrospun fibers and copolymers. Fiber structre of electrospun PHB provides large specific surface area available for biomolecular interaction. In addition, polymer coated parts of the platform inherited the premanent presence of surface carboxyl (-COOH) groups from MAA segments of the copolymer which can be effectively used for covalent and physical protein immobilization. By tuning the concentration of MAA monomers in polymerization reaction the concentration of surface -COOH groups can be carefully controlled. Therefore two different techniques have been used for immobilization of the dengue antibody aimed for dengue detection: physical attachment of dengue antibodies to the surface and covalent immobilization of antibodies through carbodiimide chemistry. In that perspective, several different characterization techniques were employed to investigate the new polymeric fiber platform such as scanning electron microscopy (SEM), atomic force microscopy (AFM), water contact angle (WCA) measurement and UV-vis titration. Regardless of the immobilization techniques, substantially higher signal intensity was recorded from developed platform in comparison to the conventional ELISA assay.
  19. Thio TH, Ibrahim F, Al-Faqheri W, Moebius J, Khalid NS, Soin N, et al.
    Lab Chip, 2013 Aug 21;13(16):3199-209.
    PMID: 23774994 DOI: 10.1039/c3lc00004d
    A technique known as thermo-pneumatic (TP) pumping is used to pump fluids on a microfluidic compact disc (CD) back towards the CD center against the centrifugal force that pushes liquids from the center to the perimeter of the disc. Trapped air expands in a TP air chamber during heating, and this creates positive pressure on liquids located in chambers connected to that chamber. While the TP air chamber and connecting channels are easy to fabricate in a one-level CD manufacturing technique, this approach provides only one way pumping between two chambers, is real-estate hungry and leads to unnecessary heating of liquids in close proximity to the TP chamber. In this paper, we present a novel TP push and pull pumping method which allows for pumping of liquid in any direction between two connected liquid chambers. To ensure that implementation of TP push and pull pumping also addresses the issue of space and heating challenges, a multi-level 3D CD design is developed, and localized forced convection heating, rather than infra-red (IR) is applied. On a multi-level 3D CD, the TP features are placed on a top level separate from the rest of the microfluidic processes that are implemented on a lower separate level. This approach allows for heat shielding of the microfluidic process level, and efficient usage of space on the CD for centrifugal handling of liquids. The use of localized forced convection heating, rather than infra-red (IR) or laser heating in earlier implementations allows not only for TP pumping of liquids while the CD is spinning but also makes heat insulation for TP pumping and other fluidic functions easier. To aid in future implementations of TP push and pull pumping on a multi-level 3D CD, study on CD surface heating is also presented. In this contribution, we also demonstrate an advanced application of pull pumping through the implementation of valve-less switch pumping.
  20. Hosseini S, Aeinehvand MM, Uddin SM, Benzina A, Rothan HA, Yusof R, et al.
    Sci Rep, 2015;5:16485.
    PMID: 26548806 DOI: 10.1038/srep16485
    The application of microfluidic devices in diagnostic systems is well-established in contemporary research. Large specific surface area of microspheres, on the other hand, has secured an important position for their use in bioanalytical assays. Herein, we report a combination of microspheres and microfluidic disk in a unique hybrid platform for highly sensitive and selective detection of dengue virus. Surface engineered polymethacrylate microspheres with carefully designed functional groups facilitate biorecognition in a multitude manner. In order to maximize the utility of the microspheres' specific surface area in biomolecular interaction, the microfluidic disk was equipped with a micromixing system. The mixing mechanism (microballoon mixing) enhances the number of molecular encounters between spheres and target analyte by accessing the entire sample volume more effectively, which subsequently results in signal amplification. Significant reduction of incubation time along with considerable lower detection limits were the prime motivations for the integration of microspheres inside the microfluidic disk. Lengthy incubations of routine analytical assays were reduced from 2 hours to 5 minutes while developed system successfully detected a few units of dengue virus. Obtained results make this hybrid microsphere-microfluidic approach to dengue detection a promising avenue for early detection of this fatal illness.
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